1. Area of the Invention
The invention relates to steelcord, covered with a coating of a material having an electrode potential, exceeding the electrode potential of steel or having a rate of corrosion, which is less than the rate of corrosion of steel, treated with a corrosion inhibiting composition according to the invention. Another object of the invention is a process for treating steel cord with the corrosion inhibiting composition according to the invention. A further object of the invention relates to rubber articles containing steel cord, treated with a corrosion inhibiting composition according to the invention.
2. Description of the Prior Art
Corrosion inhibiting compositions, typically in the form of solutions, suspensions or emulsions are commonly employed in the metal working industry to provide improved corrosion resistance of the metal objects involved. An example of such metal objects is steel cord, which is applied in rubber articles as metal reinforcement. Corrosion of steel cord may occur in the manufacturing process, during storage and transport of the steel cord as well as during and after the application of the steel cord in the rubber articles. In this respect it is remarked that always a certain amount of moisture is present in rubber articles whereas additional moisture may penetrate the rubber articles by way of diffusion and in particular by way of hair cracks and other imperfections.
In the prior art many corrosion inhibiting compositions have been used. For instance, in DE-A 2,704,190 a method is disclosed for improving the corrosion resistance of steel cord coated with a Zr, brass or bronze layer by dipping it just long enough in a sodium nitrite or potassium nitrite solution for moistening to occur and then drying it at a temperature below 150.degree. C.
Another method for providing corrosion protection to steel cord to be embedded in rubber articles like tires is disclosed in JP 02227304 A2. According to this document the tires have interior layers containing water-absorbing polymers and exterior layers of halobutyl rubbers.
Also it is known to apply a corrosion inhibiting composition, comprising specific reaction products like the product 6[2,4-bis(allylamino)-s-triazin-6-ylamino]-2-mercaptobenzothiazole as disclosed in Example 10(B) of EP 331279 A2 to brass coated steel cord.
Further, in general, DD 118,668 A discloses corrosion inhibiting compositions comprising a carrier oil having a boiling point in the range of 100-450.degree. C. and a mixture of corrosion inhibitors soluble or solubilized in the carrier oil. Examples of suitable corrosion inhibitors are a.o.t. benzotriazole, methylbenzotriazole and sodium benzoate. In particular the corrosion inhibitors are selected in such a way that a synergistic activity is achieved. Preferred corrosion inhibitors providing both a synergistic activity and a viscosity elevating activity are metal salts of higher fatty acids, in particular stearic acid like aluminium stearate. Other preferred corrosion inhibitors are oleyl sarcosine and its amine and alkaline salts.
RU 2,009, 188 C (Derwent publication AN 94-284337) relates to a conservation-lubricant for e.g. lead-coated steel based on an emulsifier, containing mineral oil, polyethylene glycol ether of stearic acid with 6 moles of ethylene oxide, the product of oxyethylation of octadecyl alcohol with 20 moles of ethylene oxide, and the triethanolamine soap of 10-20 C synthetic fatty acids. For improving the results, the lubricant additionally contains mineral oil, benzotriazole and cobalt naphthenate.
JP 49 021 299 B (Derwent publication AN 74-47967V) discloses a corrosion inhibiting composition comprising a mineral oil, an organic salt of a higher fatty acid amine and optionally benzotriazole. Such a composition provides a corrosion protecting activity to steel cord and may apparently prevent reduction of adhesive forces between steel cord and rubber as well as reduction of sticking rate of rubber to steel cord under highly humid atmosphere.
U.S. Pat. No. 5,156,759 A refers to a lubricating composition having particular utility in gas compressors, which composition is rust-inhibited and oxidation stable and provides good lubricity at high temperature in the absence of sulfur, phosphorous and metals such as zinc (column 1, lines 43-46). More in particular the lubricating composition comprises a major proportion of a synthetic base lubricating oil, an additive solubilizer, an phenolic or amino antioxidant and a rust inhibitor/metal passivator selected from the group consisting of triazolc and alkenyl succinic acid ester rust inhibitors.
In Patent Abstracts of Japan, Vol. 015, No. 133 (JP 03 017 191 A) a corrosion inhibiting grease, i.e. not a free-flowing product at 40.degree. C., is disclosed, comprising a mixed base oil containing (A) a specific polyoxypropylene glycol monoalkyl ether and a specific alkyl substituted disphenyl ether, (B) a higher fatty acid lithium salt and (C) a metal-inactivating agent such as benzotriazole.
GB- 1,364,781 A discloses a process for improving the adhesion of steel cord to rubber after vulcanisation thereof. According to this process the steel cord--prior to its use as reinforcing means in the rubber--is treated by dipping it in a mineral oil solution containing an organic acid salt of an aliphatic amine, containing from 12 to 22 carbon atoms. Examples of such organic salts are cocoa-nut monoamine salicylic acid salt, coconut monoamine acetic acid salt and beef tallow diamine salicylic salt. Further the mineral oil may contain further ingredients conventionally used to prevent discoloration of copper alloys, for example benzotriazole.
Further U.S. Pat. No. 2,890,170 relates to organosiloxane greases, i.e. not a free-flowing product at 40.degree. C., which provide an improved metal corrosion resistance. Such greases comprise a small amount of benzotriazole and--if desired--a small amount of an anhydride of a.o.t. an alkyl succinic or alkenyl succinic acid, totally containing 8-23 carbon atoms.
As apparent from the above it is known from the prior art to apply corrosion inhibiting compositions to steel articles, in particular steel cord resulting in an improved corrosion resistance of the treated steel cord. However, such an improvement of the corrosion resistance may--after vulcanisation of the rubber--result in a considerable loss of the adherence between the steel cord and the rubber comprising the steel cord as reinforcing means.
In view of the above the invention is directed to a method for avoiding above disadvantage, i.e. to the development of a corrosion inhibiting composition which decreases the level of corrosion of the steel cord and hardly affects the adherence between the steel cord and rubber after vulcanisation thereof. Further the invention should particularly relate to compositions which are environmentally acceptable.